DESCRIPTION: The purpose of this study is to explore biochemical mechanisms that occur during obstructive sleep apnea that may affect nocturnal urine production and thus contribute to the incidence of nocturia in the elderly. It is hypothesized that the negative intrathoracic pressure generated during OSA stimulate the release of natriuretic peptides, which increase urine production. She proposes three phases of study to examine this relationship. First, she will conduct a mail survey of several hundred persons over 55 to identify the incidence of nocturia, which is defined as greater than 2 voidings per night, and its possible causes. She will ask their interest in participating in a more detailed clinical assessment and interview. From this sample, at least 60 persons with nocturia who are interested in participation in the second part of the study will be screened for the severity of their symptoms and possible causes of their nocturia. Subjects meeting the study criteria will then be invited for in-depth interviews soliciting symptoms of sleep disorders and bladder disorders. They will complete a battery of relevant questionnaires on voiding, sleep, mini mental status, and symptom distress. From this pool of subjects, 20 subjects with nocturia will be selected to participate in 24 hours of observation in the GCRC. Subjects will be selected on the basis of sleep symptom severity, 10 with mild and 10 with severe symptoms of OSA. These 20 subjects will undergo blood and urine sampling at 4 hour intervals, and polysomnography during sleep, which will include thoracic excursion, EMG, pulse oximetry, heart rate, EKG, and tibial movement. Food and fluid intake, voidings, and sodium intake will be recorded. Urine will be analyzed for cGMP, a marker of atrial natriuretic peptide (ANP) or urodilatin activity, osmolality, and sodium content. Serum will be analyzed for osmolality and avp levels. Data from the mail survey and phone interviews will analyzed using descriptive statistics to characterize the range and frequency of nocturia and severity of sleep disturbance symptoms. Statistical comparisons will be made by gender and age. Data from the clinical assessments will be analyzed using regression to identify variables predictive of reports of combined symptoms of nocturia and sleep disorders. Data from the overnight observation will be subjected to analysis of variance to determine the effect of sleep disordered breathing or oxygen desaturation on the dependent variables, urine cGMP, sodium, and volume. ANCOVA will be used to determine if serum AVP levels affect nocturnal urine output.